can someone explain the gaps in the LP system to me?

Gold V 0lp = 1550 MMR Plat V 0lp = 1850 MMR

but in the LP system i need to get to 100lp 5 times, then win at least 11 promo games (~20lp a game), that is a minimum of 720lp to rise 1 league, which hardly matches up with the 300 MMR gap